This invention relates to variable focal length or zoom lenses, and particularly to a mount and mechanism for the operation of a particular type of zoom lens.
The operation of a zoom lens can be thought of as involving two separate functions, though they occur simultaneously:
First, the entire lens is generally moved relative to the object and image to change magnification in accordance with the relationship: EQU Magnification = s'/s
wherein: s -- object distance, s' -- image distance
Second, compensation is made within the lens to refocus, or maintain in focus, the lens in accordance with the following relationship EQU (1/s) + (1/s') = 1/f
wherein: f -- lens focal length.
The compensation in focal length, step two mentioned above, is generally made by movement of one or more of the lens elements within or relative to the lens group.
In copending application Ser. No. 663,397 filed by Price and Spurles on Mar. 3, 1976, a symmetrical zoom lens is described in which the outer lens elements remain fixed relative to the lens housing and an inner pair of flint and meniscus elements on each side of the aperture is moved in unison and in symmetry with respect to the opposite pair to effect variation in lens focal length for zooming. The details of that lens are more fully set forth in the above mentioned specification which is hereby incorporated by reference in this specification.
It is an object of this invention to provide a simplified mount and mechanism for a zoom lens.
Another object of this invention is to provide an anti-backlash zoom lens mechanism.
Another object of this invention is to provide a suitable mount and mechanism for a symmetrical zoom lens.
Other objects, advantages, and features of this invention will become apparent from the following more detailed description of an exemplary embodiment given in connection with the accompanying drawing.